A typical gate driver circuit includes a plurality of cascaded shift registers, where a drive signal output terminal of each of the cascaded shift registers is connected with a corresponding gate line, and the respective shift registers input scan signals sequentially to the respective rows of gate lines on a display panel. In a shift register in the related art, an output transistor typically provides the drive signal output terminal with a high-level signal under the control of a pull-up node to output a valid scan signal, and while an image is being displayed on the display panel, the high-level signal is flowing through the same output transistor all the time, and a gate of the output transistor remains at the same bias for a long period of time, so that the characteristic of the output transistor may drift, and the service lifetime thereof may be shortened, so the stability of the shift register may be degraded, and the service lifetime thereof may be shortened, thus hindering the display panel from operating stably for a long period of time.